A coprolite is fossilized feces, a unique trace fossil providing direct evidence of ancient organisms’ diet and behavior. Unlike body fossils, coprolites offer insight into past ecosystems, helping paleontologists reconstruct food webs and understand extinct life forms.
Key External Characteristics
Identifying a coprolite often begins with its external features, which vary depending on the animal and fossilization process. Many exhibit distinct shapes like cylindrical, coiled, or irregular forms, with a spiral pattern common in those from ancient sharks or fish. Sizes range from millimeters to over 60 centimeters, with larger specimens from bigger animals. Colors are typically dark, earthy tones like browns, blacks, and grays, a result of mineralization. Surface textures can be smooth, lumpy, or display folds, striations, and digestion marks.
Internal Clues
Looking inside a coprolite reveals evidence of its biological origin. Many contain undigested fragments of the original meal, offering direct insight into an ancient animal’s diet. These inclusions might consist of bone shards, fish scales, teeth, plant material, or insect exoskeletons. The internal structure can also show a spiraled or layered pattern reflecting the animal’s digestive tract. Most coprolites are composed primarily of calcium phosphate, a mineral found in bones, and can be a distinguishing factor.
Common Discovery Environments
Coprolites are found worldwide, typically preserved within sedimentary rocks like limestone and shale. They commonly occur in environments associated with ancient lakes, rivers, swamps, or marine deposits, where conditions favored rapid burial and fossilization. Finding coprolites often happens in areas with other fossilized remains, like bones or plants, increasing the likelihood of identification.
Distinguishing from Look-Alikes
Differentiating a true coprolite from objects that merely resemble it requires careful observation. Gastroliths, stomach stones swallowed by some animals, can be mistaken for coprolites. They typically have smooth, polished surfaces and rounded edges, but lack internal organic fragments.
Pseudocoprolites are inorganic mineral concretions that superficially resemble fossilized feces. They lack internal evidence of undigested food remains or specific internal structures, being entirely inorganic.
Ordinary rocks lack the specific shapes, consistent internal structures, or organic inclusions seen in coprolites. A simple “tongue test” can sometimes help: if a suspected coprolite sticks slightly, it may indicate high calcium phosphate content. However, more mineralized specimens may not react this way. Ultimately, a combination of external morphology, internal dietary remains, and geological context provides the most reliable identification.